Compositions and processes for immersion lithography

ABSTRACT

New photoresist compositions are provided that are useful for immersion lithography. Preferred photoresist compositions of the invention comprise one or more materials that can be substantially non-mixable with a resin component of the resist. Further preferred photoresist compositions of the invention comprise 1) Si substitution, 2) fluorine substitution; 3) hyperbranched polymers; and/or 4) polymeric particles. Particularly preferred photoresists of the invention can exhibit reduced leaching of resist materials into an immersion fluid contacting the resist layer during immersion lithography processing.

The present application claims the benefit of U.S. provisionalapplication No. 60/676,762 filed May 1, 2005.

The present invention relates to new photoresist compositions that areparticularly useful in immersion lithography processes. Preferredphotoresist compositions of the invention comprises one or morematerials that can be substantially non-mixable with a resin componentof the resist. Particularly preferred photoresists of the invention canexhibit reduced leaching of resist materials into an immersion fluidcontacting the resist layer during immersion lithography processing.

Photoresists are photosensitive films used for transfer of an image to asubstrate. A coating layer of a photoresist is formed on a substrate andthe photoresist layer is then exposed through a photomask to a source ofactivating radiation. The photomask has areas that are opaque toactivating radiation and other areas that are transparent to activatingradiation. Exposure to activating radiation provides a photoinducedchemical transformation of the photoresist coating to thereby transferthe pattern of the photomask to the photoresist coated substrate.Following exposure, the photoresist is developed to provide a reliefimage that permits selective processing of a substrate.

The growth of the semiconductor industry is driven by Moore's law whichstates that the complexity of an IC device doubles on average every twoyears. This necessitates the need to lithographically transfer patternsand structures with ever decreasing feature size.

One approach to achieving smaller feature sizes is to use shorterwavelengths of light, however, the difficulty in finding materials thatare transparent below 193 nm has led to the option of using immersionlithography to increase the numerical aperture of the lens by simplyusing a liquid to focus more light into the film. Immersion lithographyemploys a relatively high refractive index fluid between the lastsurface of an imaging device (e.g., KrF or ArF stepper) and the firstsurface on a wafer or other substrate.

Extensive and proven immersion lithography systems do not yet generallyexist. Certain efforts have been made to address problems associatedwith immersion lithography. See U.S. Patent Application Publication2005/0084794. Reliable and convenient photoresist and imaging processesfor immersion lithography are clearly needed.

It would be desirable to new materials and processes for immersionphotolithograpy.

We now provide new compositions and processes for immersionphotolithography.

In one aspect, preferred photoresists of the invention may comprise:

(i) one or more resins,

(ii) a photoactive component which may suitably comprise one or morephotoacid generator compounds, and

(iii) one or more materials that are substantially non-mixable with theone or more resins. Preferably, the components (i), (ii) and (iii) aredistinct materials, e.g. not covalently linked. Preferably thephotoresist is a chemically-amplified positive resist, e.g. at least oneresin of the one or more resins of component (i) comprisesphotoacid-labile groups, such as photoacid-labile ester and/or acetalgroups.

In another aspect, preferred photoresists of the invention may comprise:

(i) one or more resins,

(ii) a photoactive component which may suitably comprise one or morephotoacid generator compounds, and

(iii) one or more materials that comprise 1) Si substitution, 2)fluorine substitution; 3) hyperbranched polymers; and/or 4) polymericparticles are substantially non-mixable with the one or more resins.Preferably, the components (i), (ii) and (iii) are distinct materials,e.g. not covalently linked. Preferably the photoresist is achemically-amplified positive resist, e.g. at least one resin of the oneor more resins of component (i) comprises photoacid-labile groups, suchas photoacid-labile ester and/or acetal groups.

Particularly preferred photoresists of the invention can exhibit reducedmigration (leaching) of photoresist components into the immersion fluidduring contact of the immersion fluid during an exposure step.Significantly, such reduced migration of photoresist materials intoimmersion fluid can be achieved without applying any type of cover orbather layer over the photoresist and interposed between the resistlayer and immersion fluid.

We have found that undesired migration of acid and/or other resistmaterials from a photoresist layer into the immersion fluid layer can beparticularly problematic. Among other things, the acid or otherphotoresist materials that migrate into the immersion fluid can damagethe exposure tool as well as reduce resolution of an image patternedinto a photoresist layer. Accordingly, the photoresists of the inventionconstitute a significant advance.

Without being bound by any theory, it is believed the one or morematerials that are substantially non-mixable with the one or more resistresins can migrate toward upper regions of an applied photoresistcoating layer and thereby inhibit migration of photoresist materials outof a resist layer into immersion fluid that contacts the resist layerduring an immersion exposure step.

As referred to herein, one or more materials that are substantiallynon-mixable with the one or more photoresist resins can be any materialadded to a photoresist that results in reduced migration or leaching ofphotoresist materials into immersion fluid. Such substantiallynon-mixable materials can be readily identified empirically by testingrelative to a control resist that has the same components as the testedphotoresist, but not the candidate substantially non-mixablematerial(s).

Suitable substantially non-mixable materials for use in photoresists ofthe invention include compositions that comprise silicon and/or fluorinesubstitution.

Preferred substantially non-mixable materials for use in photoresists ofthe invention may be in the form of particles. Such particles mayinclude polymers that are polymerized in the form discrete particles,i.e. as separate and distinct polymer particles. Such polymer particlestypically have one or more different characteristics from linear orladder polymers such as linear or ladder silicon polymers. For example,such polymer particles may have a defined size and a low molecularweight distribution. More particularly, in a preferred aspect, aplurality of the polymer particles may be employed in a photoresist ofthe invention with a mean particle size (dimension) of from about 5 to3000 angstroms, more preferably from about 5 to 2000 angstroms, stillmore preferably from about 5 to about 1000 angstroms, yet morepreferably from about 10 to about 500 angstroms, even more preferablyfrom 10 to 50 or 200 angstroms. For many applications, particularlypreferred particles have a mean particle size of less than about 200 or100 angstroms.

Additional preferred substantially non-mixable materials for use inphotoresists of the invention may have Si content, includingsilsesquioxane materials, materials with SiO₂ groups, and the like.Preferred silicon-containing substantially non-mixable materials alsoinclude polyhedral oligomeric silsesquioxanxes.

Also preferred are those substantially non-mixable materials thatcontain photoacid-labile groups, such as photoacid-labile ester oracetal groups, including such groups as described herein employed in aresin component of a chemically amplified photoresist.

Preferred substantially non-mixable materials for use in photoresists ofthe invention also will be soluble in the same organic solvent(s) usedto formulate the photoresist composition.

Particularly preferred substantially non-mixable materials for use inphotoresists of the invention also will have lower surface energy and/orsmaller hydrodynamic volume than the one or more resins of thephotoresist's resin component. The lower surface energy can facilitatesegregation or migration of the substantially non-mixable materials totop or upper portions of an applied photoresist coating layer.Additionally, relative smaller higher hydrodynamic volume also can bepreferred because it can facilitate efficient migration (higherdiffusion coefficient) of the one or more substantially non-mixablematerials to upper regions of the applied photoresist coating layer.

Preferred substantially non-mixable materials for use in photoresists ofthe invention also will be soluble or become soluble upon post exposurebake (PEB, e.g. 120° C. for 60 seconds) in photoresist developercompositions (e.g. 0.26N aqueous alkaline solution). Thus, in additionto photoacid-labile groups as discussed above, other aqueousbase-solubilizing groups may be included in the substantiallynon-mixable materials such as hydroxyl, fluoroalcohol, carboxy and thelike.

Preferred non-mixable materials include polymeric materials includinghyperbranched polymers. As referred to herein, “hyperbranched polymers”include those materials known as “hyperbranched polymers under the IUPACnomenclature. See IUPAC. Compendium of Macromolecular Nomenclature (ThePurple Book); Metanomski, W. V., Ed.; Blackwell Scientific Publications,Oxford, UK, 1991. Thus, by this nomenclature, a hyperbranched polymerhas structural repeating units (or constitutional repeating unit asreferred to by IUPAC) where such structural repeating units each has acovalent connectivity of more than two. Particularly preferredhyperbranched polymers may have minimal (e.g. less than 5, 4, 3, 2 or 1weight percent) aromatic content, or be completely free of any aromaticcontent.

Hyperbranched polymers that have one or more acrylate repeat units maybe particularly suitably for many applications.

Also preferred are polymer additives that are formed frommulti-functional acrylate monomers, e.g. acrylate monomers that havemultiple vinyl groups such as trimethypropane triacrylate (sometimesreferred to herein “TMPTA”).

In a further aspect, the invention provides methods for lithographicprocessing in an immersion exposure protocol. Preferred methods of theinvention may include the following steps:

1) apply (e.g. by spin coating) a photoresist composition of theinvention to a substrate such as a semiconductor wafer. The photoresistmay be suitably applied on the wafer surface or a material previouslyapplied over the wafer such as an organic or inorganic antireflectivecomposition, or a planarizing layer, and the like. The appliedphotoresist may be thermally treated to remove solvent carrier, e.g. atabout 120° C. or less for about 30 to 60 seconds;

3) optionally, above the photoresist composition, apply an organicbarrier composition, e.g. by spin coating;

4) exposing the overcoated photoresist layer to patterned activatingradiation with a fluid (e.g. a fluid comprising water) interposedbetween the exposure tool and the coated substrate, i e. immersionexposing the photoresist layer by a fluid layer interposed between theexposure tool and the photoresist composition layer. The interposedfluid will directly contact the photoresist layer in the absence of anybarrier composition.

Preferred imaging wavelengths of lithographic systems of the inventioninclude sub-400 nm such as I-line (365 nm), sub-300 nm wavelengths e.g.248 nm, and sub-200 nm wavelengths e.g. 193 nm. In addition to one ormore substantially non-mixable materials, particularly preferredphotoresists of the invention may contain a photoactive component (e.g.one or more photoacid generator compounds) and one or more resins thatare chosen from among:

1) a phenolic resin that contains acid-labile groups that can provide achemically amplified positive resist particularly suitable for imagingat 248 nm. Particularly preferred resins of this class include: i)polymers that contain polymerized units of a vinyl phenol and an alkylacrylate, where the polymerized alkyl acrylate units can undergo adeblocking reaction in the presence of photoacid. Exemplary alkylacrylates that can undergo a photoacid-induced deblocking reactioninclude e.g. t-butyl acrylate, t-butyl methacrylate, methyladamantylacrylate, methyl adamantyl methacrylate, and other non-cyclic alkyl andalicyclic acrylates that can undergo a photoacid-induced reaction, suchas polymers in U.S. Pat. Nos. 6,042,997 and 5,492,793, incorporatedherein by reference; polymers that contain polymerized units of a vinylphenol, an optionally substituted vinyl phenyl (e.g. styrene) that doesnot contain a hydroxy or carboxy ring substituent, and an alkyl acrylatesuch as those deblocking groups described with polymers i) above, suchas polymers described in U.S. Pat. No. 6,042,997, incorporated herein byreference; and polymers that contain repeat units that comprise anacetal or ketal moiety that will react with photoacid, and optionallyaromatic repeat units such as phenyl or phenolic groups; such polymershave been described in U.S. Pat. Nos. 5,929,176 and 6,090,526, as wellas blends of i) and/or ii) and/or iii);

2) phenolic resins that do not contain acid-labile groups such aspoly(vinylphenol) and novolak resins that may be employed in I-line andG-line photoresists together with a diazonaphthoquinone photoactivecompound and have been described e.g. in U.S. Pat. Nos. 4,983,492;5,130,410; 5,216,111; and 5,529,880;

3) a resin that is substantially or completely free of phenyl or otheraromatic groups that can provide a chemically amplified positive resistparticularly suitable for imaging at sub-200 nm wavelengths such as 193nm. Particularly preferred resins of this class include: i) polymersthat contain polymerized units of a non-aromatic cyclic olefin(endocyclic double bond) such as an optionally substituted norbornene,such as polymers described in U.S. Pat. Nos. 5,843,624, and 6,048,664;ii) polymers that contain alkyl acrylate units such as e.g. t-butylacrylate, t-butyl methacrylate, methyladamantyl acrylate, methyladamantyl methacrylate, and other non-cyclic alkyl and alicyclicacrylates; such polymers have been described in U.S. Pat. No. 6,057,083;European Published Applications EP01008913A1 and EP00930542A1; and U.S.Pat. No. 6,136,501, and iii) polymers that contain polymerized anhydrideunits, particularly polymerized maleic anhydride and/or itaconicanhydride units, such as disclosed in European Published ApplicationEP01008913A1 and U.S. Pat. No. 6,048,662, as well as blends of i) and/orii) and/or iii);

4) a resin that contains repeat units that contain a hetero atom,particularly oxygen and/or sulfur (but other than an anhydride, i.e. theunit does not contain a keto ring atom), and preferable aresubstantially or completely free of any aromatic units. Preferably, theheteroalicyclic unit is fused to the resin backbone, and furtherpreferred is where the resin comprises a fused carbon alicyclic unitsuch as provided by polymerization of a norborene group and/or ananhydride unit such as provided by polymerization of a maleic anhydrideor itaconic anhydride. Such resins are disclosed in PCT/US01/14914 andU.S. Pat. No. 6,306,554;

5) resins that contain Si-substitution including poly(silsequioxanes)and the like and may be used with an undercoated layer. Such resins aredisclosed e.g. in U.S. Pat. No. 6,803,171.

6) a resin that contains fluorine substitution (fluoropolymer), e.g. asmay be provided by polymerization of tetrafluoroethylene, a fluorinatedaromatic group such as fluoro-styrene compound, compounds that comprisea hexafluoroalcohol moiety, and the like. Examples of such resins aredisclosed e.g. in PCT/US99/21912.

Preferred photoresists of the invention include bothchemically-amplified positive-acting and negative-acting photoresists.Typically preferred chemically-amplified positive resists include one ormore resins that comprise photoacid-labile groups such asphotoacid-labile ester or acetal groups.

The invention further provides methods for forming a photoresist reliefimage and producing an electronic device using photoresists of theinvention. The invention also provides novel articles of manufacturecomprising substrates coated with a photoresist composition of theinvention.

Other aspects of the invention are disclosed infra.

As discussed above, and demonstrated in the examples which follow,particularly preferred photoresists of the invention can exhibit reducedmigration (leaching) of photoresist components into the immersion fluidduring contact of the immersion fluid during an exposure step. We alsohave surprisingly found that addition of the one or more substantiallynon-mixable materials can improve lithographic performance of aphotoresist. In particular, addition of one or more substantiallynon-mixable materials can reduce line edge roughness of a developedresist including in line-space applications. Addition of one or moresubstantially non-mixable materials also can make contact holes morecircular in contact-hole applications.

As discussed above, suitable materials of photoresists of the inventionthat are substantially non-mixable with the resist resin component canbe readily identified by simple testing. In particular, as referred toherein, preferred substantially non-mixable materials will provide adecreased amount of acid or organic material to be detected in theimmersion fluid upon use of the photoresist composition containing thecandidate material relative to the same photoresist system that isprocessed into the same manner, but in the absence of the candidatesubstantially non-mixable material(s). Detection of photoresist materialin the immersion fluid can be conducted as described in Example 2 whichfollows and includes mass spectroscopy analysis of the immersion fluidbefore and after exposure to the photoresist. In such analysis, theimmersion fluid directly contacts the tested photoresist compositionlayer for about 60 seconds during exposure. Preferably, addition of oneor more substantially non-mixable materials provides at least a 10percent reduction in photoresist material (again, acid or organics asdetected by mass spectroscopy) residing in the immersion fluid relativeto the same photoresist that does not employ such substantiallynon-mixable material(s), more preferably the one or more substantiallynon-mixable materials provides at least a 20, 50, or 100, 200, 500, or1000 percent reduction photoresist material (again, acid and/ororganics) residing in to the immersion fluid relative to the samephotoresist that does not contain the substantially non-mixablematerial(s).

As discussed above, specifically preferred substantially non-mixablematerials include Si-containing materials. Especially preferredsubstantially non-mixable materials include nanostructured compositions,which are commercially available from groups such as Hybrid Plastics(Fountain Valley, Calif.), Sigma/Aldrich, and others. Such materials mayinclude molecular silicas which have a Si—O core enveloped by organicgroups; silanols; and polymers and resins which include silsesquioxanecage-structured compounds and may be silicones, styrenics, acrylics,alicyclics such as norbornenes and others.

Particles (including organic particles) useful as substantiallynon-mixable materials include Si-containing and fluorinated materials.Such particles are commercially available, or can be readilysynthesized, e.g. by reaction of one or more monomers together with acrosslinking agent and an initiator compound if desired. The reactedmonomers may have substitution as desired e.g. fluorine, Si groups,photoacid-labile groups such as photoacid-labile esters or acetals,other base-solubilizing groups such as alcohols and the like. SeeExample 1 which follows for an exemplary synthesis of such particlesproduced with multiple distinct monomers, where one of the monomersprovides a photoacid-labile group to the resulting polymer particle.

The substantially non-mixable material(s) may be present in aphotoresist composition in relatively small amounts and still provideeffective results. For instance, the one or more substantiallynon-mixable materials may be suitable present in about 0.1 to 20 weightpercent based on total weight of a fluid photoresist composition.Suitable amounts also are provided in the examples which follow.

As discussed above, preferred photoresists for use in accordance withthe invention include positive-acting or negative-acting chemicallyamplified photoresists, i.e. negative-acting resist compositions whichundergo a photoacid-promoted crosslinking reaction to render exposedregions of a coating layer of the resist less developer soluble thanunexposed regions, and positive-acting resist compositions which undergoa photoacid-promoted deprotection reaction of acid labile groups of oneor more composition components to render exposed regions of a coatinglayer of the resist more soluble in an aqueous developer than unexposedregions. Ester groups that contain a tertiary non-cyclic alkyl carbon(e.g. t-butyl) or a tertiary alicyclic carbon (e.g. methyladamantyl)covalently linked to the carboxyl oxygen of the ester are oftenpreferred photoacid-labile groups of resins employed in photoresists ofthe invention. Acetal photoacid-labile groups also will be preferred.

Preferred photoresists of the invention typically comprise a resincomponent and a photoactive component. Preferably the resin hasfunctional groups that impart alkaline aqueous developability to theresist composition. For example, preferred are resin binders thatcomprise polar functional groups such as hydroxyl or carboxylate.Preferably a resin component is used in a resist composition in anamount sufficient to render the resist developable with an aqueousalkaline solution.

For imaging at wavelengths greater than 200 nm, such as 248 nm, phenolicresins are typically preferred. Preferred phenolic resins are poly(vinylphenols) which may be formed by block polymerization, emulsionpolymerization or solution polymerization of the corresponding monomersin the presence of a catalyst. Vinylphenols useful for the production ofpolyvinyl phenol resins may be prepared, for example, by hydrolysis ofcommercially available coumarin or substituted coumarin, followed bydecarboxylation of the resulting hydroxy cinnamic acids. Usefulvinylphenols may also be prepared by dehydration of the correspondinghydroxy alkyl phenols or by decarboxylation of hydroxy cinnamic acidsresulting from the reaction of substituted or nonsubstitutedhydroxybenzaldehydes with malonic acid. Preferred polyvinylphenol resinsprepared from such vinylphenols have a molecular weight range of fromabout 2,000 to about 60,000 daltons.

Also preferred for imaging at wavelengths greater than 200 nm, such as248 nm are chemically amplified photoresists that comprise in admixturea photoactive component and a resin component that comprises a copolymercontaining both phenolic and non-phenolic units. For example, onepreferred group of such copolymers has acid labile groups substantially,essentially or completely only on non-phenolic units of the copolymer,particularly alkylacrylate photoacid-labile groups, i.e. aphenolic-alkyl acrylate copolymer. One especially preferred copolymerbinder has repeating units x and y of the following formula:

wherein the hydroxyl group be present at either the ortho, meta or parapositions throughout the copolymer, and R′ is substituted orunsubstituted alkyl having 1 to about 18 carbon atoms, more typically 1to about 6 to 8 carbon atoms. Tert-butyl is a generally preferred R′group. An R′ group may be optionally substituted by e.g. one or morehalogen (particularly F, Cl or Br), C₁₋₈ alkoxy, C₂₋₈ alkenyl, etc. Theunits x and y may be regularly alternating in the copolymer, or may berandomly interspersed through the polymer. Such copolymers can bereadily formed. For example, for resins of the above formula, vinylphenols and a substituted or unsubstituted alkyl acrylate such ast-butylacrylate and the like may be condensed under free radicalconditions as known in the art. The substituted ester moiety, ie.R′—O—C(═O)—, moiety of the acrylate units serves as the acid labilegroups of the resin and will undergo photoacid induced cleavage uponexposure of a coating layer of a photoresist containing the resin.Preferably the copolymer will have a M_(w) of from about 8,000 to about50,000, more preferably about 15,000 to about 30,000 with a molecularweight distribution of about 3 or less, more preferably a molecularweight distribution of about 2 or less. Non-phenolic resins, e.g. acopolymer of an alkyl acrylate such as t-butylacrylate ort-butylmethacrylate and a vinyl alicyclic such as a vinyl norbornanyl orvinyl cyclohexanol compound, also may be used as a resin binder incompositions of the invention. Such copolymers also may be prepared bysuch free radical polymerization or other known procedures and suitablywill have a M_(w) of from about 8,000 to about 50,000, and a molecularweight distribution of about 3 or less.

Other preferred resins that have acid-labile deblocking groups for usein a positive-acting chemically-amplified photoresist of the inventionhave been disclosed in European Patent Application 0829766A2 of theShipley Company (resins with acetal and ketal resins) and EuropeanPatent Application EP0783136A2 of the Shipley Company (terpolymers andother copolymers including units of 1) styrene; 2) hydroxystyrene; and3) acid labile groups, particularly alkyl acrylate acid labile groupssuch as t-butylacrylate or t-butylmethacrylate). In general, resinshaving a variety of acid labile groups will be suitable, such as acidsensitive esters, carbonates, ethers, imides, etc. The photoacid labilegroups will more typically be pendant from a polymer backbone, althoughresins that have acid labile groups that are integral to the polymerbackbone also may be employed.

As discussed above, for imaging at sub-200 nm wavelengths such as 193nm, preferably a photoresist is employed that contains one or morepolymers that are substantially, essentially or completely free ofphenyl or other aromatic groups. For example, for sub-200 nm imaging,preferred photoresist polymers contain less than about 5 mole percentaromatic groups, more preferably less than about 1 or 2 mole percentaromatic groups, more preferably less than about 0.1, 0.02, 0.04 and0.08 mole percent aromatic groups and still more preferably less thanabout 0.01 mole percent aromatic groups. Particularly preferred polymersare completely free of aromatic groups. Aromatic groups can be highlyabsorbing of sub-200 nm radiation and thus are undesirable for polymersused in photoresists imaged with such short wavelength radiation.

Suitable polymers that are substantially or completely free of aromaticgroups and may be formulated with a PAG of the invention to provide aphotoresist for sub-200 am imaging are disclosed in European applicationEP930542A1 and U.S. Pat. Nos. 6,692,888 and 6,680,159, all of theShipley Company.

Suitable polymers that are substantially or completely free of aromaticgroups suitably contain acrylate units such as photoacid-labile acrylateunits as may be provided by polymerization of methyladamanatylacrylate,methyladamantylmethacrylate, ethylfenchylacrylate,ethylfenchylmethacrylate, and the like; fused non-aromatic alicyclicgroups such as may be provided by polymerization of a norbornenecompound or other alicyclic compound having an endocyclic carbon-carbondouble bond; an anhydride such as may be provided by polymerization ofmaleic anhydride and/or itaconic anhydride; and the like.

Preferred negative-acting compositions of the invention comprise one ormore materials (such as a crosslinker component e.g. an amine-basedmaterials such as a melamine resin) that will cure, crosslink or hardenupon exposure to acid, and a photoactive component of the invention.Particularly preferred negative acting compositions comprise a resinbinder such as a phenolic resin, a crosslinker component and aphotoactive component of the invention. Such compositions and the usethereof has been disclosed in European Patent Applications 0164248 and0232972 and in U.S. Pat. No. 5,128,232 to Thackeray et al. Preferredphenolic resins for use as the resin binder component include novolaksand poly(vinylphenol)s such as those discussed above. Preferredcrosslinkers include amine-based materials, including melamine,glycolurils, benzoguanamine-based materials and urea-based materials.Melamine-formaldehyde resins are generally most preferred. Suchcrosslinkers are commercially available, e.g. the melamine resins soldby American Cyanamid under the trade names Cymel 300, 301 and 303.Glycoluril resins are sold by American Cyanamid under trade names Cymel1170, 1171, 1172, urea-based resins are sold under the trade names ofBeetle 60, 65 and 80, and benzoguanamine resins are sold under the tradenames Cymel 1123 and 1125.

For imaging at sub-200 nm wavelengths such as 193 nm, preferrednegative-acting photoresists are disclosed in WO 03077029 to the ShipleyCompany.

Photoresists of the invention also may contain other materials. Forexample, other optional additives include actinic and contrast dyes,anti-striation agents, plasticizers, speed enhancers, sensitizers (e.g.for use of a PAG of the invention at longer wavelengths such as I-line(i.e. 365 nm) or G-line wavelengths), etc. Such optional additivestypically will be present in minor concentration in a photoresistcomposition except for fillers and dyes which may be present inrelatively large concentrations such as, e.g., in amounts of from 5 to30 percent by weight of the total weight of a resist's dry components.

A preferred optional additive of resists of the invention is an addedbase, e.g. a caprolactam, which can enhance resolution of a developedresist relief image. The added base is suitably used in relatively smallamounts, e.g. about 1 to 10 percent by weight relative to the PAG, moretypically 1 to about 5 weight percent. Other suitable basic additivesinclude ammonium sulfonate salts such as piperidinium p-toluenesulfonateand dicyclohexylammonium p-toluenesulfonate; alkyl amines such astripropylamine and dodecylamine; aryl amines such as diphenylamine,triphenylamine, aminophenol,2-(4-aminophenyl)-2-(4-hydroxyphenyl)propane, etc.

The resin component of resists of the invention is typically used in anamount sufficient to render an exposed coating layer of the resistdevelopable such as with an aqueous alkaline solution. Moreparticularly, a resin binder will suitably comprise 50 to about 90weight percent of total solids of the resist. The photoactive componentshould be present in an amount sufficient to enable generation of alatent image in a coating layer of the resist. More specifically, thephotoactive component will suitably be present in an amount of fromabout 1 to 40 weight percent of total solids of a resist. Typically,lesser amounts of the photoactive component will be suitable forchemically amplified resists.

The resist compositions of the invention also comprise a photoacidgenerator (i.e. “PAG”) that is suitably employed in an amount sufficientto generate a latent image in a coating layer of the resist uponexposure to activating radiation. Preferred PAGs for imaging at 193 nmand 248 nm imaging include imidosulfonates such as compounds of thefollowing formula:

wherein R is camphor, adamantane, alkyl (e.g. C₁₋₁₂ alkyl) andperfluoroalkyl such as perfluoro(C₁₋₁₂alkyl), particularlyperfluorooctanesulfonate, perfluorononanesulfonate and the like. Aspecifically preferred PAG isN-[(perfluorooctanesulfonyl)oxy]-5-norbornene-2,3-dicarboximide.

Sulfonate compounds are also suitable PAGs, particularly sulfonatesalts. Two suitable agents for 193 nm and 248 nm imaging are thefollowing PAGS 1 and 2:

Such sulfonate compounds can be prepared as disclosed in European PatentApplication 96118111.2 (publication number 0783136), which details thesynthesis of above PAG 1.

Also suitable are the above two iodonium compounds complexed with anionsother than the above-depicted camphorsulfonate groups. In particular,preferred anions include those of the formula RSO₃— where R isadamantane, alkyl (e.g. C₁₋₁₂ alkyl) and perfluoroalkyl such asperfluoro (C₁₋₁₂alkyl), particularly perfluorooctanesulfonate,perfluorobutanesulfonate and the like.

Other known PAGS also may be employed in photoresists used in accordancewith the invention. Particularly for 193 nm imaging, generally preferredare PAGS that do not contain aromatic groups, such as theabove-mentioned imidosulfonates, in order to provide enhancedtransparency.

Photoresists of the invention also may contain other optional materials.For example, other optional additives include anti-striation agents,plasticizers, speed enhancers, etc. Such optional additives typicallywill be present in minor concentrations in a photoresist compositionexcept for fillers and dyes which may be present in relatively largeconcentrations, e.g., in amounts of from about 5 to 30 percent by weightof the total weight of a resist's dry components.

The photoresists used in accordance with the invention are generallyprepared following known procedures. For example, a resist of theinvention can be prepared as a coating composition by dissolving thecomponents of the photoresist in a suitable solvent such as, e.g., aglycol ether such as 2-methoxyethyl ether (diglyme), ethylene glycolmonomethyl ether, propylene glycol monomethyl ether; propylene glycolmonomethyl ether acetate; lactates such as ethyl lactate or methyllactate, with ethyl lactate being preferred; propionates, particularlymethyl propionate, ethyl propionate and ethyl ethoxy propionate; aCellosolve ester such as methyl Cellosolve acetate; an aromatichydrocarbon such toluene or xylene; or a ketone such as methylethylketone, cyclohexanone and 2-heptanone. Typically the solids content ofthe photoresist varies between 5 and 35 percent by weight of the totalweight of the photoresist composition. Blends of such solvents also aresuitable.

Liquid photoresist compositions may be applied to a substrate such as byspinning, dipping, roller coating or other conventional coatingtechnique. When spin coating, the solids content of the coating solutioncan be adjusted to provide a desired film thickness based upon thespecific spinning equipment utilized, the viscosity of the solution, thespeed of the spinner and the amount of time allowed for spinning.

Photoresist compositions used in accordance with the invention aresuitably applied to substrates conventionally used in processesinvolving coating with photoresists. For example, the composition may beapplied over silicon wafers or silicon wafers coated with silicondioxide for the production of microprocessors and other integratedcircuit components. Aluminum-aluminum oxide, gallium arsenide, ceramic,quartz, copper, glass substrates and the like are also suitablyemployed. Photoresists also may be suitably applied over anantireflective layer, particularly an organic antireflective layer.

Following coating of the photoresist onto a surface, it may be dried byheating to remove the solvent until preferably the photoresist coatingis tack free.

The photoresist layer (with overcoated barrier composition layer, ifpresent) in then exposed in an immersion lithography system, i.e. wherethe space between the exposure tool (particularly the projection lens)and the photoresist coated substrate is occupied by an immersion fluid,such as water or water mixed with one or more additives such as cesiumsulfate which can provide a fluid of enhanced refractive index.Preferably the immersion fluid (e.g., water) has been treated to avoidbubbles, e.g. water can be degassed to avoid nanobubbles.

References herein to “immersion exposing” or other similar termindicates that exposure is conducted with such a fluid layer (e.g. wateror water with additives) interposed between an exposure tool and thecoated photoresist composition layer.

The photoresist composition layer is then suitably patterned exposed toactivating radiation with the exposure energy typically ranging fromabout 1 to 100 mJ/cm², dependent upon the exposure tool and thecomponents of the photoresist composition. References herein to exposinga photoresist composition to radiation that is activating for thephotoresist indicates that the radiation is capable of forming a latentimage in the photoresist such as by causing a reaction of thephotoactive component (e.g. producing photoacid from the photoacidgenerator compound).

As discussed above, photoresist compositions are preferablyphotoactivated by a short exposure wavelength, particularly a sub-400nm, sub-300 and sub-200 nm exposure wavelength, with I-line (365 nm),248 nm and 193 nm being particularly preferred exposure wavelengths aswell as EUV and 157 nm.

Following exposure, the film layer of the composition is preferablybaked at temperatures ranging from about 70° C. to about 160° C.Thereafter, the film is developed, preferably by treatment with anaqueous based developer such as quaternary ammonium hydroxide solutionssuch as a tetra-alkyl ammonium hydroxide solution; various aminesolutions preferably a 0.26 N tetramethylammonium hydroxide, such asethyl amine, n-propyl amine, diethyl amine, di-n-propyl amine, triethylamine, or methyldiethyl amine; alcohol amines such as diethanol amine ortriethanol amine; cyclic amines such as pyrrole, pyridine, etc. Ingeneral, development is in accordance with procedures recognized in theart.

Following development of the photoresist coating over the substrate, thedeveloped substrate may be selectively processed on those areas bared ofresist, for example by chemically etching or plating substrate areasbared of resist in accordance with procedures known in the art. For themanufacture of microelectronic substrates, e.g., the manufacture ofsilicon dioxide wafers, suitable etchants include a gas etchant, e.g. ahalogen plasma etchant such as a chlorine or fluorine-based etchant sucha Cl₂ or CF₄/CHF₃ etchant applied as a plasma stream. After suchprocessing, resist may be removed from the processed substrate usingknown stripping procedures.

The following non-limiting examples are illustrative of the invention.

EXAMPLE 1 Particle Additive Preparation

A preferred fluorinated particle additive is prepared as follows:

A reactor vessel is charged with a desired amount of propylene glycolmonomethyl ether acetate (PGMEA) and heated to 80° C. with N₂ purge. Thefollowing monomers (PFPA, ECPMA, TMPTA), cross-linker and initiator(t-amyl peroxypivalate) are mixed in PGMEA at 80 to 90 weight % fluidcomposition in an ice bath. The initiator content is 4% relative to thetotal amount of monomers and cross-liker. The monomers were used in thefollowing weight amounts: 70 weight % pentafluoracrylate (PFPA), 20weight % ethyl cyclopentyl methacrylate (ECPMA), and 10 weight %(trimethypropane triacrylate (TMPTA):

That monomer/crosslinker/initiator/PGMEA mixture is then fed into thereactor vessel in a course of 90 minutes. After the addition to thereactor vessel is complete, the temperature of mixture within thereactor vessel is held at 80° C. for 30 minutes. Then, an additional 2weight % (relative to the total monomers and cross-linker) of initiatoris fed into the reactor. 30 minutes later, another 2 weight % (relativeto the total monomers and cross-linker) of initiator is fed into thereactor. After that addition, the temperature of the mixture within thereactor vessel is held at 80° C. for additional 2 hours. Thereafter, thetemperature of the reactor vessel is permitted to cool to roomtemperature.

By that procedure, polymer particles were provided that had anumber-average molecular weight (Mn) of 7088 and a weight-averagemolecular weight (Mw) of 19255.

EXAMPLE 2 Photoresist Preparation and Processing

A photoresist composition is prepared by admixing the followingmaterials in the specified amounts:

1. Resin component: Terpolymer of (2-methyl-2-adamantylmethacrylate/beta-hydroxy-gamma-butyrolactonemethacrylate/cyano-norbornyl methacrylate in an amount of 6.79 weight %based on total weight of the photoresist composition;2. Photoacid generator compound: T-butyl phenyl tetramethylene sulfoniumperfluorobutanesulfonate in an amount of 0.284 weight % based on totalweight of the photoresist composition;3. Base additive: N-Alkyl Caprolactam in an amount of 0.017 weight %based on total weight of the photoresist composition;4. Surfactant: R08 (fluorine-containing surfactant, available fromDainippon Ink & Chemicals, Inc.) in an amount of 0.0071 weight % basedon total weight of the photoresist composition5. Substantially non-mixable additive: fluorinated PFPA/ECPMA/TMPTAterpolymer particle having Mn of 7088 and Mw of 19255 prepared asdescribed in Example 1 above and in an amount of 0.213 weight % based ontotal weight of the photoresist composition.6. Solvent component: propylene glycol monomethyl ether acetate toprovide about a 90 percent fluid composition.

A control photoresist composition also is prepared that has the samecomponents and amounts thereof as the above photoresist composition, butthe control photoresist does not contain a substantially non-mixableadditive.

Both the control photoresist composition and above photoresistcomposition containing were spin-coated onto silicon wafers, dried onvacuum hotplate to remove soft-plate and then exposed in an immersionlithography process with aqueous immersion fluid directly contacting thedried photoresist layers. In that immersion system, the photoresistlayers were exposed to patterned 193 nm radiation at a dose of 24.1mJ/cm² for the control photoresist layers and 23.4 mJ/cm² for thephotoresist composition layers that contained the substantiallynon-mixable additive.

The photoresist layers were then post-exposed baked (such as at about120° C.) and developed with 0.26N alkaline aqueous developer solution toprovide well-resolved 90 nm 1:1 lines and spaces.

To evaluate leaching of resist components, the following protocol wasutilized: 1 ml of deionized (DI) water was placed on the resist surfacein a confined area (42 cm²) for 60 seconds. The DI water was thencollected for LC/MS analysis to determine the amount of photoacidgenerator compound (PAG) leached. The control photoresist resulted in 21ppb of the photoacid generator compound and degradation products in theimmersion fluid. The above photoresist composition that contained asubstantially non-mixable additive (i.e. fluorinated PFPA/ECPMA/TMPTAterpolymer particles) had 0.21 ppb of the photoacid generator compoundand degradation products in the immersion fluid.

EXAMPLE 3 Photoresist Preparation and Processing

A photoresist composition is prepared by admixing the followingmaterials in the specified amounts:

1. Resin component: Terpolymer of (2-methyl-2-adamantylmethacrylate/beta-hydroxy-gamma-butyrolactonemethacrylate/cyano-norbornyl methacrylate in an amount of 6.79 weight %based on total weight of the photoresist composition;2. Photoacid generator compound: T-butyl phenyl tetramethylene sulfoniumperfluorobutanesulfonate in an amount of 0.284 weight % based on totalweight of the photoresist composition;3. Base additive: N-Alkyl Caprolactam in an amount of 0.017 weight %based on total weight of the photoresist composition;4. Surfactant: R08 (fluorine-containing surfactant, available fromDainippon Ink & Chemicals, Inc.) in an amount of 0.0071 weight % basedon total weight of the photoresist composition5. Substantially non-mixable additive: isooctyl polyhedralsilsesquoioxane (IPSS) obtained from Hybrid Plastics in an amount of0.213 weight % based on total weight of the photoresist composition.6. Solvent component: propylene glycol monomethyl ether acetate toprovide about a 90 percent fluid composition.

A control photoresist composition also is prepared that has the samecomponents and amounts thereof as the above photoresist composition, butthe control photoresist does not contain a substantially non-mixableadditive.

Both the control photoresist composition and above photoresistcomposition containing were spin-coated onto silicon wafers, dried onvacuum hotplate to remove soft-plate and then exposed in an immersionlithography process with aqueous immersion fluid directly contacting thedried photoresist layers. In that immersion system, both the controlphotoresist layers and the photoresist composition layers that containedthe substantially non-mixable additive were exposed to patterned 193 nmradiation at a dose of 26.5 mJ/cm².

The photoresist layers were then post-exposed baked (such as at about120° C.) and developed with 0.26N alkaline aqueous developer solution toprovide well-resolved 90 nm 1:1 lines and spaces.

To evaluate leaching of resist components, the following protocol wasutilized:1 ml of DI water was placed on the resist surface in a confinedarea (4.2 cm²) for 60 seconds. The DI water was then collected for LC/MSanalysis for the amount of PAG leached. The control photoresist resultedin 16.4 ppb of the photoacid generator compound and degradation productsin the immersion fluid. The above photoresist composition that containeda substantially non-mixable additive (i.e. isooctyl polyhedralsilsesquoioxane (IPSS)) had 1.76 ppb of the photoacid generator compoundin the immersion fluid.

EXAMPLES 4-6 Additional Photoresist Leaching Testing

Additional photoresists were prepared corresponding with to thephotoresists of Example 1 above, but with differing amounts of thesubstantially non-mixable additive of isooctyl polyhedralsilsesquoioxane (IPSS, obtained from Hybrid Plastics) as a percentage oftotal solids. These photoresists were lithographically processed andimmersion exposed at 193 nm as described in Example 3 above andevaluated for leaching of photoacid generator compound and degradationproducts thereof (in parts per billion or ppb) as described in Example3. Contact angles of the photoresist layers also were evaluated. Resultsare set forth in the following Table 1.

TABLE 1 Weight Percent Amount of photo- Contact IPSS in photo- acidgenerator Angle of Example resists to leached into deionized No. totalsolids immersion fluid water 4 1 percent 2.52 ppb 104.1° 5 2 percent2.21 ppb 106.4° 6 3 percent 1.76 ppb 105.4° Comparative 0 percent 17.0ppb 72.2°

The photoresists of Examples 4-6 also provided well-resolvedlines/spaces.

EXAMPLES 7-19 Additional Polymer Additives for Photoresists inAccordance with the Invention

In the following Examples 7-19, the polymers were synthesized by thegeneral procedures of Example 1 above, using the corresponding monomersin the amounts in the below Examples to produce the formed polymers.

EXAMPLE 7

A branched tetrapolymer was prepared having the following repeat unitsin the respective molar amounts: x/y/z/TMPTA=70/15/5/10, wherein asshown in the immediately below structure the monomer providingpolymerized x-units is PFPA (pentafluoropropyl ecrylate), the monomerproviding polymerized y-units is ECPMA (ethylcyclopentyl methacrylate),and the monomer providing polymerized z-units is acrylic acid.

EXAMPLE 8

A hyperbranched tetrapolymer was prepared having the following repeatunits in the respective molar amounts: with x/y/z/TMPTA=70/15/5/10,wherein repeat units x, y and z are shown in the immediately belowstructure. As can be seen from that structure, the monomer polymerizedto provide z-units is methacrylic acid.

EXAMPLE 9

A hyperbranched terpolymer was prepared having the following repeatunits in the respective molar amounts: x/y/TMPTA=70/20/10, whereinrepeat units x and y are shown in the immediately below structure.

EXAMPLE 10

A hyperbranched terpolymer was prepared having the following repeatunits in the respective molar amounts: with x/y/TMPTA=80/10/10, whereinrepeat units x and y are shown in the immediately below structure.

EXAMPLE 11

A linear copolymer was prepared having the following repeat units in therespective molar amounts: y/z=94/6, wherein repeat units y and z areshown in the immediately below structure. As can be seen from thatstructure, the monomer polymerized to provide y-units is tert-butylmethacrylate.

EXAMPLE 12

A linear copolymer was prepared having the following repeat units in therespective molar amounts: y/z=94/6, wherein repeat units y and z areshown in the immediately below structure. As can be seen from thatstructure, the monomer polymerized to provide z-units is carboxyethylacrylate.

EXAMPLE 13

A linear homopolymer was prepared consisting of polymerized tert-butylmethacrylate groups.

EXAMPLE 14

A linear copolymer was prepared having the following repeat units in therespective molar amounts: y/z=50/50, wherein repeat units y and z areshown in the immediately below structure. As can be seen from thatstructure, the monomer polymerized to provide z-units is1-cyclohexyl-3-hydroxy-4,4,4-trifluoro-3-(trifluoromethyl)butyl2-methacrylate.

EXAMPLE 15

A linear copolymer was prepared having the following repeat units in therespective molar amounts: y/z=50/50, wherein repeat units y and z areshown in the immediately below structure. As can be seen from thatstructure, the monomer polymerized to provide z-units is 2-methacrylicacid 4,4,4-trifluoro-3-hydroxy-1-methyl-3-trifluromethyl-butyl ester.

EXAMPLE 16

A linear copolymer was prepared having the following repeat units in therespective molar amounts: y/z=70/30, wherein repeat units y and z areshown in the immediately below structure. As can be seen from thatstructure, the monomer polymerized to provide z-units is 2-methacrylicacid 4,4,4-trifluoro-3-hydroxy-1-methyl-3-trifluromethyl-butyl ester.

EXAMPLE 17

A hyperbranched terpolymer was prepared having the following repeatunits in the respective molar amounts: with y/z/TMPTA=70/30/10, whereinrepeat units x and y are shown in the immediately below structure.

EXAMPLE 18

A linear copolymer was prepared having the following repeat units in therespective molar amounts: y/z=50/50, wherein repeat units y and z areshown in the immediately below structure. As can be seen from thatstructure, the monomers polymerized to provide z-units are 5 and6[3,3,3-trifluoro-2-hydroxy-2-(trifluoromethyl)propyl]bicycle[2,2,1]hept-2-ylacrylate.

EXAMPLE 19

A linear terpolymer was prepared having the following repeat units inthe respective molar amounts: with y/z1/z2=74/20/6=50/50, wherein repeatunits y, z1 and z2 are shown in the immediately below structure.

EXAMPLES 20-33 Immersion Leaching Analysis

In the following Examples 20-31, in three different 193 nm photoresists(referred to as first-type, second-type, third-type) polymers of theabove Examples 7-18 were added in amounts specified in the below Table2. The three photoresist compositions (i.e. first-type, second-type,third-type) were each positive chemically-amplified resists thatcontained non-aromatic resin with photoacid-labile ester groups andseparate photoacid generator compounds. In comparative Examples 32 and33, a further additive (such as polymer) was not added to the first-typeand second-type resists. In Table 2 below, references to wt. % relativeto total solid means all composition components except solvent carrier.

Leaching analysis was conducted as follows described in Example 3 aboveand the below Table 2. Results are set forth in Table below.

TABLE 2 Barrier layer results (leaching analysis) PAG Leaching, Exam-Polymer mole/cm², ple of Exam- Polymer admixed in amount and 60 secondsNo. ple No. used in specified photoresist Leaching 20 7 3 wt. %(relative to total solid) 9.67⁻¹³ in first-type 193 nm photoresist 21 83 wt. % (relative to total solid) 5.08⁻¹³ in first-type 193 nmphotoresist 22 9 2 wt. % (relative to total solid) 1.05⁻¹² insecond-type 193 nm photoresist 23 10 3 wt. % (relative to total solid)1.19⁻¹² in first-type 193 nm photoresist 24 11 3 wt. % (relative tototal solid) 2.42⁻¹² in third-type 193 nm photoresist 25 12 3 wt. %(relative to total solid) 1.84⁻¹² in third-type 193 nm photoresist 26 133 wt. % (relative to total solid) <8.06⁻¹⁴ in third-type 193 nmphotoresist 27 14 3 wt. % (relative to total solid) 3.87⁻¹³ inthird-type 193 nm photoresist 28 15 3 wt. % (relative to total solid)1.85⁻¹³ in third-type 193 nm photoresist 29 16 2 wt. % (relative tototal solid) 7.66⁻¹³ in second-type 193 nm photoresist 30 17 3 wt. %(relative to total solid) 9.67⁻¹³ in third-type 193 nm photoresist 31 183 wt. % (relative to total solid) 1.95⁻¹² in third-type 193 nmphotoresist 32 No First-type 193 nm photoresist 1.21⁻¹¹ (compar-additional without additional polymer added ative) polymer 33 NoSecond-type 193 nm photoresist 3.06⁻¹¹ (compar- additional withoutadditional polymer added ative) polymer

EXAMPLES 34-45 Water Contact Angle Analysis

Water contact angles were evaluated for the spin-coated layers of thepolymers as specified in Table 3 below. Several water contact angleswere evaluated: static, receding, advancing, sliding, developer staticin general accordance with the procedures disclosed in Burnett et at, J.Vac. Sci. Techn. B, 23(6), pages 2721-2727 (November/December 2005).Results are set forth in Table 3 below.

The results of these Examples 34-45 also show that photoresistcompositions of the invention can be prepared to achieve desired waterangles, as may be desired by device manufacturers, such as a recedingwater contact angle of in excess of 70 and/or a sliding water contactangle of less than 20.

TABLE 3 Polymer Exam- of DI water contact angles ple Example θ θ θ θdeveloper No. No. static receding advancing sliding θ static 34 7 87 6198 40 35 8 84 25 148 50 36 9 94 75 100 28 37 10 85 54 97 50 38 11 84 7388 16 78 39 12 85 75 89 15 79 40 13 86 80 90 11 87 41 14 91 78 93 17 8142 15 89 78 92 16 84 43 16 88 81 92 17 83 44 17 85 78 90 13 79 45 18 8574 89 17 79

1. A method for processing a photoresist composition, comprising: (a)applying on a substrate a photoresist composition comprising: (i) one ormore resins, (ii) a photoactive component, and (iii) one or morematerials that are substantially non-mixable with the one or moreresins; and (b) immersion exposing the photoresist layer to radiationactivating for the photoresist composition.
 2. The method of claim 1wherein the one or more substantially non-mixable materials areparticles.
 3. The method of claim 1 wherein the one or moresubstantially non-mixable materials comprise aqueous base-solubilizinggroups and/or one or more photoacid-labile groups.
 4. The method ofclaim 1 wherein the one or more substantially non-mixable materialscomprise 1) Si substitution, 2) fluorine substitution and/or 3) arehyperbranched polymers.
 5. (canceled)
 6. A coated substrate systemcomprising: a substrate having thereon: a coating layer of a photoresistcomposition, the photoresist composition comprising: (i) one or moreresins, (ii) a photoactive component, and (iii) one or more materialsthat are substantially non-mixable with the one or more resins.
 7. Thecoated substrate system of claim 6, wherein the (iii) one or morematerials comprise 1) Si substitution, 2) fluorine substitution; 3)hyperbranched polymers; and/or 4) polymeric particles.
 8. The system ofclaim 6 wherein an immersion lithography fluid contacts the top surfaceof the photoresist coating layer.
 9. The system of claim 6 furthercomprising an immersion lithography apparatus.
 10. A photoresistcomposition comprising: one or more resins, (ii) a photoactivecomponent, and (iii) one or more materials that are substantiallynon-mixable with the one or more resins, and/or one or more materialsthat comprise 1) Si substitution, 2) fluorine substitution; 3)hyperbranched polymers; and/or 4) polymeric particles.